Investigation of the role of back contact work function for hole transporting layer free perovskite solar cells applications

Abstract

Despite the unprecedented progress in power conversion efficiency (PCE), perovskite solar cells (PSCs) have a weak link where the organic hole transport materials are prone to degrade under stress (humidity, temperature etc.), leading to the overall device performance downfall. Hole transport layer (HTL) free perovskite solar cells could be one of the options to overcome this challenge. In HTL-free PSCs, new, suitable back contact materials are needed to further optimize the device's performance and stability by investigating the work function of back contact materials. In this study, SCAPS-1D software is used to understand the role of the back contact material work function on device performance. The optimized devices with a back contact work function of 5.4 eV or above showed a power conversion efficiency of over 22%. In addition, the effects of bulk defects, interfacial defects, and series resistance in HTL-free PSCs are also studied. It is found that defects heavily affect the solar cell characteristics, and the VOC falls rapidly with increasing defects density. On the other hand, the series resistance does not affect the VOC and JSC; however, the fill factor and PCE diminish steadily with an increase in series resistance. This study will pave the way for HTL free perovskite solar cells fabrication work to reduce the overall cost of the device.