New Organic and Inorganic Functional Materials for Photovoltaic Applications: Synthesis, Characterization, and Device Performance Studies

Abstract

Over the past three decades, the dye-sensitized solar cell (DSSC) and perovskite solar cell (PSC), which belong to the third-generation solar cells have emerged as an attractive, and promising photovoltaic technologies due to their superior performance, lightweight, flexibility, eco-friendly nature, and low manufacturing costs. On this basis, in the present work, the attention has been focused on the three areas of solar cell research, viz. new organic n-/p-type dyes as sensitizers/co-sensitizers for DSSCs, new organic hole-transport materials for PSCs, and solvent selection as well as the development of large-area carbon-based PSCs. Based on the detailed literature survey, thirty-four new metal-free n-type dyes, viz. n-K1- 34, and eight p-type dyes, viz. p-K35-42 were designed as potential sensitizers/co-sensitizers for DSSC applications. Also, two new organic molecules (h-K43-44) were designed as possible HTMs for PSCs. All of them were successfully synthesized and characterized. Further, they were subjected to in-depth optical, electrochemical, theoretical, and photovoltaic studies. From these studies, it is clear that the synthesized molecules possess all the prerequisites to act as sensitizers/HTMs in the devices. Amongst the n-type molecules, the dye n-K5 displayed the optimum PCE of 2.44 % as a sensitizer and n-K6 dye showcased an improved PCE of 8.81 % as co-sensitizer along with Ru-based HD-2 sensitizer. The photovoltaic results of p-type molecules disclose that the p-K36-based DSSC showed PCE of 0.031 %, comparable with that of benchmark reference P1. Furthermore, among the newly synthesized HTMs, the h-K43 displayed a better PCE of 2.55 % in PSCs. To sum up, by further optimizing the molecular structure of dyes/HTMs it is possible to further ameliorate the photovoltaic performance of devices. Further, a detailed investigation was carried out on the selection of appropriate solvent for a single-step deposition of mixed-cation perovskite in carbon-based PSCs (C-PSCs) using the Lewis acid-base adduct approach. Strikingly, the device fabricated using DMSO solvent yielded the highest PCE of 12.33%. In continuation, the highly efficient and stable large-area C-PSCs have been developed using CsBr modified mp-TiO2 as a superior electron transport material, with PCE 12.59% (active area 0.7 cm2) and 11.55 % (active area 70 cm2). Conclusively, this exploration is expected to provide deeper insights for the further scaling-up of carbon-based PSCs with improved efficiency and stability for their future commercial applications.