Correlation between charge carriers mobility and nanomorphology in a blend of P3HT/PCBM bulk heterojunction solar cell: Impact on recombination mechanisms

Abstract

Sandwich configurations consisting of hole-only and electron-only devices are employed to study the transport properties of polymer/fullerene blended material. Upon thermal annealing at 150 °C and subsequent device characterisations a direct correlation between solar cell device power conversion efficiency and charge carrier mobilities is identified. The highest power conversion efficiency reported herein resulted from the electron to hole mobility ratio of 4.78. This ratio further reduces to 0.357 at 175 °C as a result of the deterioration in electron mobility at the same time as enhancement in hole carrier mobility with no further improvement in PCE. Effects of thermal annealing on trap density, reveals that the trap assisted recombination is more dominant as compared to the bimolecular recombination. Furthermore such a mechanism enhances as a result of increasing trap density at higher annealing temperatures. Effect of light intensity on the open circuit voltage VOC further verifies that the dominant recombination process is through trap assisted recombination.

Characterizing Electric Field Exposed P3HT Thin Films Using Polarized‐Light Spectroscopies

“…Studies directed toward reducing structural disorder and, thus, increasing carrier mobility are fundamental to enhancing the efficiency of these materials. Thermal annealing, solvent annealing, slow growth, epitaxy, and the use of shear forces, high boiling solvents and solvent additives have been explored as a means to attenuate the problem. Electric fields have previously been used to align or to generate a particular morphology of nanomaterials .…”

Effect of Blend Composition on Bulk Heterojunction Organic Solar Cells: A Review

“…From this body of literature, it is clear that the optimum blend composition for P3HT:PCBM organic solar cells is different from that of the PPV:PCBM system. The optimum composition appears to be close to 50 wt.% PCBM . A large list of reported performance characteristics and corresponding optimal blend compositions for P3HT:PCBM organic solar cells is displayed in Table .…”

Formulation strategies for optimizing the morphology of polymeric bulk heterojunction organic solar cells: a brief review

“…The organization of polymer chains has been shown to greatly impact the charge carrier mobility and therefore the recombinations in OSCs. 36,37 This can be explained by the fact that charge transport, occurring by holes hopping from chain to chain, relates exponentially to the hopping distance and thus to the interchain spacing. In OSCs, the charge carrier mobility is an important factor to optimize: both high mobility and a balance between electron and hole mobilities were shown to be beneficial.…”

“…In OSCs, the charge carrier mobility is an important factor to optimize: both high mobility and a balance between electron and hole mobilities were shown to be beneficial. 36,[38][39][40][41] For some polymers, an increase in crystallinity is also generally accompanied by a modification in their UV-visible absorption spectra. For example, P3HT exhibits a red shift and the appearance of additional vibronic bands when the degree of crystallinity increases in the BHJ.…”