Impact of Alkyl-Based Side Chains in Conjugated Materials for Bulk Heterojunction Organic Photovoltaic Cells—A Review

Abstract

The research for efficient organic materials organized in bulk heterojunction (BHJ) thin films for organic photovoltaics (OPVs) has shown a significant breakthrough in the past decade. Desired structural organization can be attained through various strategies. In this regard, the current review highlights tuning of alkyl chains introduced on molecular structures of active materials. The recent wide literature is classified based on the introduction of alkyl chains on polymers and small molecules used as donor and acceptor materials. The design of these materials, the morphological aspects of the active layers, and the performances of the related photovoltaic cells are detailed. A comprehensive discussion on chemical structures of the different material families considered, their modification by alkyl chains of various natures, and the morphological aspects are reported and tabulated.

Alkylsilyl-substituted benzodithiophene-based small molecules as promising hole-transport materials for perovskite solar cells

“…The same effect from introducing alkylsilyl groups was observed in previous works. 36,37 However, the loading of four triisopropylsilyl groups in TB-Si 3-3 resulted in some increase of the HOMO energy up to −5.27 eV. We note that the HOMO levels of TB-Si 3-3 and TB-Si 4-3 match well with the valence band of MAPbI 3 (−5.43 eV) 38 , which is beneficial for hole extraction from the perovskite layer.…”

Energy‐Level Alignment and Electronic Structure of Dual‐State Luminogens Thin Films

“…In Q‐type aggregation the molecules are quasi‐isolated in the solid state, in which situation the photophysical properties of the molecules are only minorly affected by the aggregation effect. Alkyl side chains are used to control substrate‐induced thin film structures [ 19–21 ] as well as solid‐state aggregation [ 22 ] and, indeed, even though the terminal alkoxyl chains in NICS‐X only have minor difference in length, NICS‐M and NICS‐B are of the quasi‐isolated Q‐type, but H‐aggregation takes place for NICS‐E and the latter leads to a large redshift in the PL peak position in the solid state compared to the solution. [ 17 ] On the basis of these interesting features, NICS‐X is a perfect model system to explore substrate effects on the optical and electronic properties of organic thin films.…”

Dibenzofulvene Derivatives as Promising Materials for Photovoltaic and Organic Electronics

“…Thanks to this, electricity consumption in urban agglomerations can be significantly reduced. Solar cells using organic compounds are an extremely interesting solution that has been intensively researched recently [7,9,12,[15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. These include, among others, dye-sensitized solar cells (DSSCs) [16][17][18]25,26], perovskite solar cells (PVSs) [7,9,12,27,28], or even bulk heterojunction solar cells (BHJ) [15,19,20,29,30].…”

“…Solar cells using organic compounds are an extremely interesting solution that has been intensively researched recently [7,9,12,[15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. These include, among others, dye-sensitized solar cells (DSSCs) [16][17][18]25,26], perovskite solar cells (PVSs) [7,9,12,27,28], or even bulk heterojunction solar cells (BHJ) [15,19,20,29,30]. Many of the tested cells of this type can be installed in unusual places in buildings, such as windows or facades.…”