Planar D-\(\pi\)-A Configured Dimethoxy Vinylbenzene Based Small Organic Molecule for Solution-Processed Bulk Heterojunction Organic Solar Cells  
[PERSON]  
1 Energy Materials & Surface Science Laboratory, Solar Energy Research Center, School of Chemical Engineering, Jeonbuk National University, Jeonju 54896, Korea; [EMAIL_ADDRESS] (S.A.); [EMAIL_ADDRESS] (A. ); [EMAIL_ADDRESS] (E.-B.K. )1 Energy Materials & Surface Science Laboratory, Solar Energy Research Center, School of Chemical Engineering, Jeonbuk National University, Jeonju 54896, Korea; [EMAIL_ADDRESS] (S.A.)1 Energy Materials & Surface Science Laboratory, Solar Energy Research Center, School of Chemical Engineering, Jeonbuk National University, Jeonju 54896, Korea; shabaz@jbnu. many optoelectronic devices due to their distinctive features, such as their flexibility, light weight, low temperature processing and potentially low cost over conventional silicon solar cells [10; 11; 12; 13; 14]. The photophysical and electrochemical properties of SOMs are highly tunable by designing and configuring chemical molecular structures [15]. One can assume that the appropriate selection of D-A moieties in SOMs can significantly enhance the charge mobility and contribute a large interfacial area for charge separation and collection [16]. Appreciable attention has recently been focused on exploring new small organic materials for the optimization of PCE and understanding the fundamental mechanism with the structure-property-performance relationship. Generally, low band gap SOMs with increased short circuit currents (Jsc) and minimum voltage loss are considered as deciding factors to maximizing photovoltaic (PV) performance [17]. The donor materials with deep HOMO levels (low ionization potential) are possible choices for obtaining a greater open circuit voltage (Voc) without sacrificing Jsc in BHJ-OSCs [18]. To boost the absorption and electronic properties of SOMs, \(\pi\) electron systems in D-A or A-D-A based SOMs are helpful for accelerating charge mobility and rectifying the light absorption from the visible region to the NIR region [19]. The presence of a \(\pi\) bond system or \(\pi\)-spacers pushes more to break exciton or free charge carriers upon light absorption in an active layer [20]. SOMs based on \(\pi\)-conjugated electron systems have recently gained attention, owing to their high electron affinity and low ionization potentials, which define their donors and acceptors, respectively. The push-pull effect in donor-acceptor with \(\pi\)-conjugation arrangements can enable a fast intramolecular and photoinduced charge transfer, extend absorption in the visible region and ambipolar charge transport properties with high, balanced mobility can be observed in \(\pi\)-conjugated D-\(\pi\)-A systems [21; 22; 23; 24]. In our previous report, [PERSON] et al. inserted an ethylene system as a \(\pi\)-spacer in D-A-D type SOMs and demonstrated a PCE of about 3.53%, with an improved fill factor (FF) = \(\sim\)0.58, Jsc = \(\sim\)8.71 mA/cm\({}^{2}\) and \(\sim\)Voc of 0.698 V [25]. [PERSON] et al. reported the synthesis of D-\(\pi\)-D type SOMs in which fluorene units behaved as \(\pi\)-spacers and displayed a reasonable PCE of \(\sim\)2.13% [26]. The donor materials exhibited the deep HOMO levels for matching the energy level offset of PC\({}_{61}\)BM acceptor. Additionally, thiophene units as \(\pi\)-linkers in SOMs also played a vital role in gaining excellent optoelectronic properties [27]. In this report, D-\(\pi\)-A SOM 25-(3,5-dimethoxyxystyryl) thiophen-2-yl) methylene-1H-indene-1,3(2H)-dione, named as DVB-T-ID, has been synthesized and utilized as donor material for BHJ-OSCs. 2,3-Dihydro-1H-indene-1,3-dione (ID) acts as a potent acceptor moiety in various SOMs due to its stronger polarity and increased dielectric constant, and it displays a large interaction with the dimethoxy vinylbenzene (DVB) donor template [28; 29].