## 1 Introduction  
The conversion efficiency of crystalline silicon solar cells strongly depends on the carrier recombination behavior [1; 2; 3]. The recombination properties of the diffusion region and depletion region are related to light injection levels, i.e., cumulative integrated irradiance. Characterizing the recombination for solar cells under different injection levels is very important to maximize the outdoor performance of solar cells and accurately model daily energy production under non-standard test conditions [4; 5; 6]. However, clarifying the recombination parameters in different regions of a solar cell is very complicated, particularly for solar cells with different technologies and under different injection levels [7; 8; 9]. [PERSON] et al. made a contribution to the theory of carrier generation-recombination in the space-charge region of a p-n junction, where the recombination behavior can be expressed by the reverse saturation current density [10]. [PERSON] and [PERSON] estimated the emitter saturation current density by measuring the effective lifetime [11]. [PERSON] et al. gave an advanced model of the effective minority carrier lifetime for passivated crystalline silicon wafers [12]. [PERSON] et al. studied carrier transportation and surface passivation in solar cells [13]. [PERSON] et al. made a contribution on metal contact recombination [14]. [PERSON] et al. studied the origin of the apparently reduced recombination parameter of highly doped regions [15; 16; 17]. Other authors have used the measured current-voltage (I-V) characteristics of solar cells in conjunction with computer simulations to obtain the recombination parameters in solar cells under equilibrium conditions [18; 19; 20; 21; 22]. However, recently, [PERSON] indicated that the reverse saturation current density of a solar cell under illumination differs from that in equilibrium. He thought that the reverse saturation current density should be called the recombination parameter when a solar cell is illuminated [23]. Although some researchers ever investigated the recombination parameters of solar modules using a double-diode model, the estimated parameter of a solar module could not reflect the recombination behavior of a solar cell accurately, owing to soldering and encapsulation [24; 25; 26; 27; 28; 29]. People often understand the recombination behavior of solar cells by measuring minority carrier lifetime and modeling, but it is generally not possible to detangle recombination in the different regions for solar cells [30]. To date, almost no one has studied the recombination parameter \(J_{01}\) of the diffusion region and the recombination parameter \(J_{02}\) of the depletion region for full-area aluminum back surface field (Al-BSF) and passivated emitter and rear cell (PERC) silicon solar cells under different injection levels [31; 32; 33]. Few studies have been conducted on the recombination parameters and their effect on the output performance of solar cells that change with the injection level. At present, the PERC silicon solar cell and the Al-BSF silicon solar cell are the two main structures in the photovoltaic industry. Although Al-BSF silicon solar cells and PERC solar cells feature a homogeneous emitter on the front side, the structure of PERC solar cells is slightly different from that of Al-BSF solar cells. The recombination behavior of PERC solar cells is different from that of Al-BSF solar cells when the two types of solar cells are biased in the forward direction [34; 35; 36; 37]. A quantitative analysis of recombination behavior for PERC solar cells and Al-BSF solar cells under different injection levels is very important for process optimization and device modeling. In this paper, incorporating the measured current density-voltage characteristic under different injection levels, the recombination parameters of the diffusion region and the depletion region and their effect on output performance are investigated for Al-BSF silicon solar cells and PERC silicon solar cells for the first time.