Exploring the Limits and Balancing Efficiency, Transparency, and Esthetics in Ultrathin a-Si:H Transparent Photovoltaic Devices

Abstract

Transparent photovoltaic (TPV) devices represent a promising advance in photovoltaic technologies, particularly in building-integrated photovoltaics (BIPV). Unlike conventional photovoltaics, which primarily prioritize efficiency, TPV must balance between efficiency, transparency, and aesthetics. These additional dimensions introduce unique challenges on device architecture. This article reports the development of wide-bandgap, inorganic-based TPV devices integrating ultrathin hydrogenated amorphous silicon (a-Si:H) as a transparent absorber, with carrier selective contacts and transparent electrodes. The article analyzes how absorber thickness influences the electrical, optical, and aesthetic performance of devices, evaluating key parameters in TPV such as light utilization efficiency (LUE), average photopic transmittance (APT), color rendering index (CRI), and electrical properties such as power conversion efficiency (PCE). The device structure is SLG/FTO/AZO/a-SiC_x(n)/a-Si:H/V₂O_x/AZO. This approach results in PCE ranging from 1.7% with an APT of 60% to a PCE of 4.1% with an APT of 28%, yielding LUE values between 0.9% and 1.3%. Device characterization encompasses optical spectrophotometry, J–V measurements under standard test conditions, spectral response analysis, and variable illumination measurements (VIM). Additionally, color characterization is conducted using CIE 1931 color space maps to determine the chromaticity coordinates, CRI, and the variation of color as a function of absorber thickness.