Enhanced Selective Contact Behavior in a-Si:H/oxide Transparent Photovoltaic Devices via Dipole Layer Integration

Abstract

Transparent photovoltaic (TPV) devices have the potential to revolutionize photovoltaic (PV) technology by enabling on-site generation while minimizing visual impact. However, a major challenge in the development of TPV, as well as for many PV technologies, is the open-circuit voltage (Voc) deficit, which limits their efficiency. In this work, the development of wide-bandgap inorganic-based TPV devices is reported with a focus on low-cost, earth-abundant, stable, and nontoxic materials. The device structure consists of an ultrathin hydrogenated amorphous silicon (a-Si:H) absorber and metal-oxide layers as selective contacts. Herein, novel approach is presented to significantly improve device performance, especially in Voc, by introducing molecular dipoles in the device electron transport layer. By incorporating polyethyleneimine or poly(amidoamine) G1 and G2 dipoles, Voc (from 410 mV up to 638 mV) is significantly increased without sacrificing the average photopic transmittance of the device, leading to a record efficiency for this particular approach in TPV. Measurements confirm excellent long-term stability. This approach can potentially allow tuning the work function of the selective contacts enabling the use of low-cost, earth-abundant materials that are not optimized for a particular absorber. Furthermore, this solution circumvents the issue of low Voc by a simple interface treatment.