Environmentally friendly cathode interlayer modification on edible bio‐acids with enhanced electron extraction and improved power conversion efficiency

Abstract

Realizing environmental compatibility and high power conversion efficiency (PCE) are crucial in the research of organic photovoltaics towards practical application. Applying environmentally friendly bio-materials into the modification of cathode interlayer (CIL) is a feasible approach to move towards both targets. In this research, three edible bio-acids, ursolic acid, citric acid, and malic acid, are employed to modify the PDIN CIL of the organic solar cells (OSCs) with non-fullerene acceptors. Among these edible bio-acid modifiers, ursolic acid shows its excellent performance in improving interfacial contact and suppressing charge recombination. It helps to obtain a good interfacial contact and facilitates the electron extraction. As a result, the photovoltaic performance is significantly improved. The average PCE are increased from 17.58% of the control devices to 18.35% of the PDIN + Ursolic Acid based devices, with a maximum PCE of 18.54%. It is the champion efficiency among the reported applications of bio-derived materials for the CILs. This study demonstrates the successful application of edible bio-acid, which offers an effective and green approach for the CIL modification to realize highly efficient OSCs.cathode interlayer, edible bio-acid, organic solar cell, PDIN | INTRODUCTIONOrganic solar cells (OSCs) own unique merits such as lightweight, high degree of flexibility and ease of possessing, which is a promising renewable technology. In the Junjie Wen and Rui Lin contributed equally to this work.

Quinquethiophene-based fully nonfused electron acceptors towards efficient organic solar cells via side-chain engineering

“…[1][2][3] In recent years, owing to the development of fused ring electron acceptors (FREAs), especially the ITIC-series with an acceptor-donor-acceptor (A-D-A) structure and Y-series with an A-DA 0 D-A structure, the power conversion efficiencies (PCEs) of single-junction OSCs have exceeded 19%. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] However, the large rigid ladder-type fused ring cores in these efficient FREAs generally require multiplestep synthesis and purification, resulting in high synthetic costs of acceptors, which has been considered as one of the major obstacles to large-scale production. Nonfused electron acceptors have emerged as potential alternatives for achieving cost-effective OSCs due to their concise synthesis, high stability and low cost.…”

Revealing the AcOH-Induced Dissolution Mechanism of Alcohol-Soluble Interlayers

“…These CIMs facilitate energy-level alignment at the electrode interface and create an interfacial dipole for ohmic contact. − Therefore, resolving the imperceptible but significant challenge in an alcohol-soluble organic CIMs-based ETL is an efficient approach for improving the performance of OSCs. Among the myriad of alcohol-soluble CIMs with varied molecular structures, neutral amino-containing compounds, such as PFN and PDIN, are extensively utilized in organic electronic devices. − However, the limited solubility of these interlayers necessitates the addition of trace amounts of acetic acid (AcOH) to enhance their dissolution in highly polar solvents. − Previous reports have proposed a somewhat ambiguous solubilization theory, suggesting that the tertiary amine groups of PFN and PDIN undergo an acid–base reaction with AcOH, forming quaternary ammonium salts that enable their dissolution in methanol. , Additionally, some studies suggest that AcOH can significantly impact the orientation and magnitude of the interfacial dipole, establishing a built-in electrostatic potential that enhances the short-circuit current and open-circuit voltage. , However, detailed mechanistic studies of how neutral interfacial layers acquire solubility in polar solvents induced by AcOH are relatively lacking.…”