Charge Carrier Dynamics in a Ternary Bulk Heterojunction System Consisting of P3HT, Fullerene, and a Low Bandgap Polymer

Abstract

The photoresponse of P3HT:PC 61 BM based organic solar cells can be enhanced by blending the bulk heterojunction with the low band gap polymer Si-PCPDTBT. Organic solar cells containing the resulting ternary blend as the photoactive layer deliver short circuit currents of up to 15.5 mA cm − 2 . Morphological studies show modest phase separation without the perturbation of the crystallinity of the P3HT:PC 61 BM matrix, in accordance with the measured acceptable fi ll factors. Picosecond time-resolved pump-probe spectroscopy reveals that the sensitization of P3HT:PC 61 BM with Si-PCPDTBT involves the transfer of photogenerated positive polarons from the low band gap polymer to P3HT within few hundreds of picoseconds. Intensity dependent experiments in combination with global fi tting show that the charge transfer from Si-PCPDTBT to P3HT competes with non-geminate charge carrier recombination of the holes in the Si-PCPDTBT phase with electrons in the PC 61 BM phase, both processes being of diffusive nature. At excitation densities corresponding to steady state conditions under one sun, modelling predicts hole transfer effi ciencies exceeding 90%, in accordance with IQE measurements. At higher pump intensities, bimolecular recombination suppresses the hole transfer process effectively. 950 wileyonlinelibrary.com

Charge carrier transport properties in ternary Si-PCPDTBT:P3HT:PCBM solar cells

“…An increase in V oc is observed with increasing the Si-PCPDTBT content of the blends, which could be originating from the lower lying HOMO levels of Si-PCPDTBT with respect to P3HT [10]. Such a trend of increasing open circuit voltages has been reported in analogous ternary blends consisting of Si-PCPDTBT [8]. The short circuit currents are found to increase initially with the 20% donor loading of Si-PCPDTBT, i. e. a ratio of 0.2:0.8:1, respectively, for Si-PCPDTBT:P3HT:PCBM, which then reduces with a further increase in the Si-PCPDTBT content.…”

“…The morphology of the resulting system and hence the bimolecular recombination losses largely affect the photovoltaic performance of such systems [7]. Unlike the P3HT:PCBM system, the majority of low bandgap polymers exhibit the Langevin type recombination when blended with PCBM [8]. Therefore, while the addition of low bandgap polymers to the P3HT:PCBM system improves the absorption, it can also disrupt the highly ordered morphology of P3HT:PCBM blend.…”

Synthesis and Properties of Hexa(4-tert-butylphenoxy) Substituted [30]Trithiadodecaazahexaphyrin and its Metal Complexes

“…[1,2] Moreover, presence of three thiadiazole subunits makes these compounds promising candidates for a wide area of applications, similar to other thiadiazole-containing polymers and small molecules that find their use in medicinal, agricultural [8] and photovoltaic sectors. [9,10] With the goal of detailed characterization and revealing potential applications of this young class of compounds, substituted and unsubstituted thiadiazoloporphyrinoids have been obtained very recently. [3,7,11,12] It has been found that unsubstituted thiadiazoloporphyrinoids are insoluble in most of organic solvents.…”

Recent Developments in Quantum Dots/CNT Co-Sensitized Organic Solar Cells

“…Various sensitizers based on low band gap polymers [55][56][57][58][59][60][61][62][63], small molecules [64][65][66], dyes [67][68][69] and nanoparticles [13][14][15][16][17][18][19][20][21] are employed in the structure of the photoactive layer in combination with donor material which is usually consists of a large bandgap polymer and fullerene derivative as acceptor. Recently, the record PCEs over 12% have been reported for the PBDB-T:IT-M: BisPC 70 BM (1:1:0.2) ternary solar cells with a Jsc=17.3 mA/cm², Voc=0.95 V and FF=74% [42], which demonstrate the potential of ternary sensitization concept for OPVs' upscaling.…”