Solution-Processed Squaraine Bulk Heterojunction Photovoltaic Cells

Abstract

The donor, 2,4-bis[4-(N,N-diisobutylamino)-2,6-dihydroxyphenyl] squaraine (SQ) is used with the acceptor, [6,6]-phenyl C70 butyric acid methyl ester (PC70BM) to result in efficient, solution-processed, small-molecule bulk heterojunction photovoltaic cells. The distribution of the donor nanoparticles in the acceptor matrix as a function of relative concentrations results in a trade-off between exciton dissociation and hole mobility (and hence, cell series resistance). A bulk heterojunction solar cell consisting of an active region with a component ratio of SQ to PC70BM of 1:6 has a power conversion efficiency of 2.7 +/- 0.1% with a 8.85 +/- 0.22 mA/cm(2) short-circuit current density and an open-circuit voltage of 0.89 +/- 0.01 V obtained under simulated 1 sun (100 mW/cm(2)) air mass 1.5 global (AM1.5 G) solar illumination. This is a decrease from 3.3 +/- 0.3% at 0.2 sun intensity, and is less than that of a control planar heterojunction SQ/C60 cell with 4.1 +/- 0.2% at 1 sun, suggesting that the nanoparticle morphology introduces internal resistance into the solution-based thin film. The nanomorphology and hole mobility in the films is strongly dependent on the SQ-to-PC70BM ratio, increasing by greater than 2 orders of magnitude as the ratio increases from 28% to 100% SQ.

A hybrid CMOS-imager with a solution-processable polymer as photoactive layer

“…To demonstrate the ease of switching the material system to extend the absorption to the NIR region, we added a SQ dye 12,[44][45][46] as additional donor material to the PCBM:P3HT solution to exploit the absorption spectrum of SQ between 600 and 900 nm. About solar cells and photodetectors with a bulk-heterojunction active layer of PCBM:SQ, it was already reported [44][45][46] . In the Supplementary Discussion we report about the fabrication of large scale reference photodetectors to determine an optimal mixing ratio for a PCBM:P3HT:SQ detector.…”

Layer‐by‐Layer Processed Organic Solar Cells

“…Fused acenes [34][35][36][37][38][39][40][41][42][43] and several famous classes of dyes, such as phthalocyanine (Pc), [20, subphthalocyanine (SubPc), [66][67][68][69][70][71] subnaphthalocyanine (SubNc), [72,73] merocyanine (MC), [74] cyanine dyes, [75][76][77][78][79] and squaraine (SQ), [80][81][82][83] are widely used in LL vacuum deposited OPVs (Figure 2, Table 1). In 2001, Forrest and Peumans fabricated bilayer heterojunction OPVs based on CuPc and C 60 with a PCE of 3.6% under 150 mW cm −2 simulated AM1.5G illumination.…”

“…[74] Squaraine (SQ) dyes have also shown tremendous potential for LL processed OPVs because of intense absorption in the red and near-infrared spectral regions, ambient stability and non-toxicity. [80][81][82][83] In 2009, Forrest and co-workers reported a vacuum deposited bilayer OPV based on SQ dye DIB-SQ and C 60 with a PCE of 3.2%. [81] Fused acenes especially pentacene have also been widely studied as donor materials in LL vacuum deposited OPVs due to their high hole mobility, broad absorption and good thermal stability.…”

Solvent‐Annealed Crystalline Squaraine: PC70BM (1:6) Solar Cells

“…Hence, under standard simulated solar illumination conditions (100 mW/cm 2 , AM1.5G spectrum), the effi ciency was limited to only ∼ 3%. [ 10 ] In this work, we explore annealing of these SQ:PC 70 BM (1:6) blends in solvent vapor to create continuous crystalline (and hence low resistance) pathways for hole conduction through the rareifi ed SQ environment. We note that, while spin-casting of these mixtures provides a simple means to prepare homogeneous thin fi lms, rapid solvent evaporation does not allow for suffi cient molecular reorganization, which is needed to achieve an equilibrium, crystalline, and uniformly phase-separated mixture.…”