Query: Organic tandem solar cells comprising polymer and small-molecule subcells

Candidate papers:

abstract: In this work the authors report monolithic organic tandem solar cells. The front cell is fabricated from a blend of poly(3 hexylthiophene 2,5 diyl) and [6,6] phenyl C61 butyric acid methyl ester while a copper phthalocyanine/fullerene (CuPc/C60) bilayer is used for the back cell. An intermediate recombination zone is realized using two doped organic semiconductor layers and a thin noble metal interlayer. The active polymer layer thickness is optimized to ensure matching of the subcell currents. The open circuit voltage Voc=1V nearly reaches the sum of the open circuit voltages of each contributing cell.
author_names: Alexander Colsmann

Johannes Junge

Christian Kayser

Uli Lemmer
title: Organic tandem solar cells comprising polymer and small molecule subcells
year: 2006

abstract: In this study, we stacked a small molecule based cell onto another polymer based device to fabricate a tandem organic solar cell that extended the absorption range of the entire cell over a wider spectral range. Between the two subcells, we positioned a connecting structure comprising layers of Cs2CO3, Ag and MoO3. Current matching phenomena played an important role in determining the device efficiency. The judicious selection of subcells exhibiting superior current matching improved the performance of the tandem cell. Indeed, in the optimally performing tandem cells we obtained both a high open circuit voltage (1.21V) and an improved power conversion efficiency (1.81% From analyses of the surface morphology and transmission spectra of the middle Ag layers, we deduced that the main function of this film was to provide more sites for efficient recombination of holes and electrons. The thickness of this layer was limited by its transmittance. A thinner Ag layer allowed more light to be harvested by the top cell, increasing the overall performance of the tandem cell. (Some figures in this article are in colour only in the electronic version)
author_names: Fang-Chung Chen

Cheng-hao Lin
title: Construction and characteristics of tandem organic solar cells featuring small molecule based films on polymer based subcells
year: 2010

abstract: Multilayer structures involving solution deposited polymer films are difficult to fabricate, not allowing for unrestricted designs of polymer based optoelectronic devices required for maximizing their performance. Here, we fabricate a hybrid organic tandem solar cell whose top and bottom subcells have polymer:fullerene and small molecules active layers, respectively, by a solvent free process based on transferring the polymer:fullerene layer from an elastomeric stamp onto a vacuum deposited bottom subcell. The interface between small molecule and transferred polymer:fullerene layers is void free at the nanoscale, allowing for efficient charge transport across the interface. Consequently, the transfer fabricated tandem cell has an open circuit voltage (VOC) almost identical to the sum of VOC values for the single junction devices. The short circuit current density (JSC) of the tandem cell is maximized by current matching achieved by varying the thickness of the small molecule active layer in the bottom subcell, which is verified by numerical simulations. The optimized transfer fabricated tandem cell, whose active layers are composed of poly[2,1,3 benzothiadiazole 4,7 diyl[4,4 bis(2 ethylhexyl) 4H cyclopenta[2,1 b:3,4 b']dithiophene 2,6 diyl][6,6] Phenyl C71 butyric acid methyl ester and Di [4 (N,N di p tolyl amino) phenyl]cyclohexane:C70, has VOC 1.46 V, JSC 8.48 mA/cm2, a fill factor of 0.51, leading to the power conversion efficiency of 6.26% the highest among small molecule polymer:fullerene hybrid tandem solar cells demonstrated so far.
author_names: Yoonseok Ka

Hyejin Hwang

Changsoon Kim
title: Hybrid Organic Tandem Solar Cell Comprising Small Molecule Bottom and Polymer:Fullerene Top Subcells Fabricated by Thin Film Transfer
venue: Scientific Reports
year: 2017

abstract: Polymer/small molecule parallel connected tandem organic solar cells are explored as a simple platform for high efficiency tandem solar cells that are not subject to complications associated with complex current matching or successive solution processing. In particular, MoOx/Ag/MoOx (MAM) trilayer electrodes are investigated as an intermediate electrode that connects a front subcell composed of a solution processed bulk heterojunction of poly{2,6' 4,8 di(5 ethylhexylthienyl) benzo[1,2 b;3,4 b]dithiophene alt 5 dibutyloctyl 3,6 bis(5 bromothiophen 2 yl)pyrrolo[3,4 c]pyrrole 1,4 dione} (PBDTT DPP) and the fullerene derivative [6,6] phenyl C61 butyric acid methyl ester (PCBM) and a back subcell composed of a thermally evaporated C70 layer doped with 1,1 bis (4 bis(4 methyl phenyl) amino phenyl) cyclohexane (TAPC) The effect of each MoOx layer is analyzed in terms of both optical and electrical properties. A joint theoretical and experimental study indicates that the electric field is distributed along the cell depth such that the photogenerated current of the front subcell depends on the thickness of both MoOx layers, with a varied interference effect, and that of the back subcell depends primarily on the thickness of the adjacent MoOx layer, with a varied cavity resonance effect. Based on optimized conditions of MAM electrodes, parallel tandem hybrid organic solar cells having higher power conversion efficiency than that of single junction cells are successfully realized.
author_names: Soohyun Lee

Tae Eui Kang

Donggeon Han

Hoyeon Kim

Bumjoon J Kim

Jongjin Lee

Seunghyup Yoo
title: Polymer/small molecule parallel tandem organic solar cells based on MoOx Ag MoOx intermediate electrodes
year: 2015

abstract: Three furan fused boron dipyrromethenes (BODIPYs) with a CF3 group on the meso carbon are synthesized as near infrared absorbing materials for vacuum processable organic solar cells. The best single junction device reaches a short circuit current (jsc) of 13.3 mA cm 2 and a power conversion efficiency (PCE) of 6.1% These values are highly promising for an electron donor material with an absorption onset beyond 900 nm. In a tandem solar cell comprising a NIR BODIPY subcell and a matching "green" absorber subcell, complementary absorption is achieved, resulting in PCE of ~10%
author_names: Tian-Yi Li

Toni Meyer

Zaifei Ma

Johannes Benduhn

Christian Korner

Olaf Zeika

Koen Vandewal

Karl Leo
title: Small Molecule Near Infrared Boron Dipyrromethene Donors for Organic Tandem Solar Cells.
venue: Journal of the American Chemical Society
year: 2017

abstract: Combining wide and narrow band gap absorbers in tandem solar cells is a promising approach to improve the energy conversion of sun light. In this work, we present hybrid tandem devices comprising monolithically connected copper indium gallium diselenide (CIGS) bottom cells and polymer top cells. The thin polymer:fullerene bulk heterojunction absorber layers were transferred onto the rough CIGS surface by a soft contact lamination technique. Sputtered or solution deposited top cathodes complete the tandem devices with enhanced open circuit voltages.
author_names: Manuel Reinhard

Paul Sonntag

Ralph Eckstein

Linda Burkert

Andreas Bauer

Bernhard Dimmler

Uli Lemmer

Alexander Colsmann
title: Monolithic hybrid tandem solar cells comprising copper indium gallium diselenide and organic subcells
year: 2013

abstract: The rapid development of perovskite solar cells is beyond our imagination. The power conversion efficiency (PCE) of organic inorganic hybrid perovskite solar cells has reached 25.5% (https:/www.nrel.gov/pv/cell efficiency.html) However, the unsatisfactory stability of hybrid perovskites is an obstacle for their commercialization, which results from the volatile and hygroscopic organic cations[1] Recently, inorganic perovskites (CsPbIxBr3 x) are receiving more and more attention due to their good thermal stability[2] Among them, CsPbI2Br is the most popular material for solar cells due to the appropriate Goldschmidt tolerance factor[3, 4] But the photovoltaic performance of CsPbI2Br is much lower than many other perovskites due to its large bandgap (1.92 eV) which means it can only absorb the light below 650 nm, leading to low photocurrent[5] Narrow bandgap organic solar cells have much broader photoresponse than CsPbI2Br solar cells, but their relatively high energy loss and insufficient absorption for the short wavelength light limit their PCE. Making tandem solar cells is an effective approach to break the efficiency limit. Tandem solar cells based on perovskite/silicon[6] perovskite/Cu(In,Ga)Se2 (CIGS)[7] perovskite/perovskite[8] and perovskite/organic[9] structures have been reported. Compared with perovskite/silicon and perovskite/CIGS tandem cells, perovskite/perovskite and perovskite/organic tandem cells have the advantage of low temperature solution processing. Perovskite/perovskite tandem solar cells with tin containing perovskite cell as the rear cell offered a certified PCE of 24.2% which is the highest PCE for perovskite/perovskite tandem solar cells so far[8] But it is hard to obtain long term stable tincontaining perovskites because Sn2+ is easy to be oxidized to Sn4+ Recently, the fast development of organic solar cells with narrow bandgap non fullerene acceptors provides new choice for tandem cells[10] After we reported the first two terminal inorganic perovskite/organic tandem solar cells[5] the PCE of inorganic perovskite/organic tandem cells increased from 15.04% to 18.38%[11] via using better perovskite and organic subcells. But the PCEs are still much lower than the other perovskite based tandem cells, which may be due to the lack of high performance organic solar cells. Recently, we developed a new polymer donor D18 for organic solar cells, demonstrating a PCE of 18.56% which is the highest PCE for organic solar cells to date[12, 13] Introducing high performance D18:Y6 cells into inorganic perovskite/organic tandem cells may further improve the PCE. In this communication, we report an inorganic perovskite/organic tandem solar cell with a CsPbI2Br front cell and a D18:Y6 rear cell. The energy loss in the tandem cell was reduced by using SnO2/ZnO electron transport layer. We optimized the photocurrent matching of the two subcells by adjusting the thickness of CsPbI2Br layer and D18:Y6 layer. The tandem solar cells delivered a record PCE of 20.18% The active layer for the organic solar cells consists of a wide bandgap polymer D18 (Eg 1.98 eV)[12] and a narrow bandgap non fullerene small molecule Y6 (Eg 1.81 eV)[14] (Fig. 1(a) The D18:Y6 blend film presents an absorption peak at 810 nm and an absorption onset at 931 nm (Fig. 1(b) The CsPbI2Br film shows an absorption onset at 650 nm and a shoulder peak at 628 nm. CsPbI2Br can compensate the absorption of D18:Y6 below 628 nm, leading to better light harvesting when applied in a tandem structure. The CsPbI2Br cells and D18:Y6 cells (Fig. S1) were fabricated to find the suitable charge transport materials and preparation conditions. Unlike the frequently used SnO2, SnO2/ZnO was used as electron transport layer. The CsPbI2Br cells with SnO2/ZnO electron transport layer show enhanced open circuit voltage (Voc) and short circuit current density (Jsc) (Fig. S2) suggesting reduced energy loss in the cells. The best CsPbI2Br cell and D18:Y6 cell gave PCEs of 14.48% and 15.23% respectively (Fig. S3 and Table S1) The CsPbI2Br cells show external quantum efficiency (EQE) above 80% at 390 640 nm (Fig. S3(b) The high EQE before 640 nm and high Voc for CsPbI2Br cell make it suitable to be the front cell in a tandem cell. The D18:Y6 cell presents broad photoresponse up to 970 nm, leading to high integrated current density (23.43 mA cm 2) than the CsPbI2Br cell (14.56 mA cm 2) The high EQE of D18:Y6 cell beyond 640 nm makes it suitable to be the rear cell. The tandem cells were fabricated with the structure shown in Fig. S4(a) The SnO2/ZnO layer, CsPbI2Br layer, PTAA/MoO3/Au/ZnO nanoparticles (ZnO NPs) interconnecting layer (ICL) D18:Y6 layer, and MoO3/Ag layer can be seen clearly in the cross section scanning electron microscopy (SEM) image of the tandem cell (Fig. 1(c) The thicknesses for CsPbI2Br layer and D18:Y6 layer are 260 and 120 nm, respectively. The thin Au layer (1 nm) between the two subcells is important for reducing the charge transport barrier, thus improving device performance[5] The charge transport layers form a
author_names: Zuo Xiao

Chuantian Zuo

Liming Ding
title: Inorganic perovskite/organic tandem solar cells with efficiency over 20%
year: 2021

abstract: The paucity of near infrared (NIR) organic materials with high absorption at long wavelengths, combined with large diffusion lengths and charge mobilities, is an impediment to progress in achieving high efficiency organic tandem solar cells. Here a subcell is employed within a series tandem stack that comprises a solution processed ternary blend of two NIR absorbing nonfullerene acceptors and a polymer donor combined with a small molecular weight, short wavelength fullerene based subcell grown by vacuum thermal evaporation. The ternary cell achieves a power conversion efficiency of 12.6 0.3% with a short circuit current of 25.5 0.3 mA cm 2 an open circuit voltage of 0.69 0.01 V, and a fill factor of 0.71 0.01 under 1 sun, AM 1.5G spectral illumination. The success of this device is a result of the nearly identical offset energies between the lowest unoccupied molecular orbitals (LUMOs) of the donors with the highest occupied molecular orbital (HOMO) of the acceptor, resulting in a high open circuit voltage. A tandem structure with an antireflection coating combining these subcells demonstrates a power conversion efficiency of 15.4 0.3%
author_names: Yongxi Li

Jiu-Dong Lin

Xiao Liu

Yue Qu

Fu-Peng Wu

Feng Liu

Zuo-Quan Jiang

Stephen R Forrest
title: Near Infrared Ternary Tandem Solar Cells.
venue: Advanced materials
year: 2018

abstract: Abstract Organic tandem solar cells were investigated using modeling and simulation methods to determine the optimal structural design and to predict device efficiencies. Each tandem structure comprised two subcells composed of varying combinations of low and high bandgap donor polymers and acceptor fullerene materials. The subcell employing the low bandgap polymer, poly[2,6 (4,4 bis (2 ethylhexyl) 4H cyclopenta[2,1 b;3,4 b']dithiophene) alt 4,7 (2,1,3 benzothiadiazole) (PCPDTBT) was combined with either C 61 or C 71 based acceptor fullerene [6,6] phenyl C 61/71 butyric acid methyl ester PC 61/71 BM) Similarly, a subcell employing the high bandgap polymer, poly(3 hexylthiophene) (P3HT) was modeled after including either PC 61 BM or PC 71 BM components. The mutual effects of both subcells in tandem were analyzed to determine such parameters as current density, open circuit voltage, fill factor, and power conversion efficiency. Our results indicate that appropriate spatial ordering of the subcells can allow achievement of device efficiencies exceeding 9%
author_names: Patrick M Boland

Keejoo Lee

James Dean

Gon Namkoong
title: Design of organic tandem solar cells using low and high bandgap polymer:fullerene composites
year: 2010

abstract: The emerging field of stacked layers (double and even multi layers) in organic photovoltaic cells is reviewed. Owing to the limited absorption width of organic molecules and polymers, only a small fraction of the solar flux can be harvested by a single layer bulk heterojunction photovoltaic cell. Furthermore, the low charge carrier mobilities of most organic materials limit the thickness of the active layer. Consequently, only part of the intensity of the incident light at the absorption maximum is absorbed. A tandem or multi junction solar cell, consisting of multiple layers each with their specific absorption maximum and width, can overcome these limitations and can cover a larger part of the solar flux. In addition, tandem or multi junction solar cells offer the distinct advantage that photon energy is used more efficiently, because the voltage at which charges are collected in each subcell is closer to the energy of the photons absorbed in that cell. Recent developments in both small molecule and polymeric photovoltaic cells are discussed, and examples of photovoltaic architectures, geometries, and materials combinations that result in tandem and multi junction solar cells are presented.
author_names: Afshin Hadipour

Bert de Boer

Paul W M Blom
title: Organic tandem and multi junction solar cells
year: 2008