Solution-Processed Semitransparent CZTS Thin-Film Solar Cells via Cation Substitution and Rapid Thermal Annealing

摘要

Semitransparent solar cells are able to capitalize on land scarcity in urbanenvironments by co-opting windows and glass structures as power generators,thereby expanding the capacity of photovoltaics to meet energy needs. To besuccessful, devices must be efficient, possess good visual transparency, longtermstability, and low cost. Copper zinc tin sulfide is a promising thin-filmmaterial that consists of earth-abundant elements. For optical transparency, theusual molybdenum back contact is replaced with a transparent conducting oxide(TCO). However, due to subsequent high-temperature annealing, the TCOdegrades, losing conductivity, or forms a poor interface with CZTS. Lowertemperatures mitigate this issue but hinder grain growth in CZTS films. Herein,cadmium substitution and silver and sodium doping are used to aid grain growthand improve film quality at lower annealing temperatures. Thin molybdenum issputtered on TCO to help improve the interface transition postannealing byconversion to MoS_2. Rapid thermal processing is used to minimize hightemperatureexposure time to preserve the TCO. With these methods, a semitransparentdevice with a front illumination efficiency of 2.96% is demonstrated.