Investigation of HTL-free perovskite solar cell under LED illumination: interplay between energy bandgap and absorber optimization

Abstract

In this paper, we introduce an efficient perovskite solar cell (PSC) designed for indoor applications, which does not incorporate a hole transport layer (HTL). The perovskite material studied in this work is MAPbI3-xClx, whose bandgap energy can be adjusted to match the spectrum of white LEDs. While the removal of the HTL initially leads to a decline in cell performance, a subsequent enhancement is achieved in performance when the work function of the rear contact is increased. This improvement can be attributed to the increased electric field at the back contact interface. The performance of the HTL-free PSC is further optimized by adjusting various technological and physical factors of the perovskite absorber. These parameters include thickness, bulk defects, doping level, and energy gap of the perovskite material. Our results demonstrate that the HTL-free PSC structure exhibits superior performance metrics under a white LED environment at 1000 lux and a color temperature of 2700 K. In this context, a power conversion efficiency (PCE) above 34% can be obtained upon proper optimization procedures. Further, the interplay between the energy gap (Eg) of the absorber and the optimization procedures is investigated, highlighting its importance in the context of HTL-free designs for indoor applications. Practical recommendations stemming from this study include an emphasis on optimization for HTL-free cells and caution against applying ideal Eg ranges to non-optimized configurations.