Decreased Recombination Through the Use of a Non‐Fullerene Acceptor in a 6.4% Efficient Organic Planar Heterojunction Solar Cell

Abstract

An optimization of several aspects of planar heterojunction solar cells based on boron subnaphthalocyanine chloride (SubNc) as a donor material is presented. The use of hexachlorinated boron subphthalocyanine chloride (Cl6SubPc) as an alternative acceptor to C60 allows for the simultaneous increase of the short‐circuit current, fill factor, and open‐circuit voltage compared to cells with fullerene acceptors. This is due to the complementary absorption of Cl6SubPc versus SubNc, reduced recombination at the heterointerface, and improved energetic alignment. Furthermore, insertion of a thin diindeno[1,2,3‐cd:1′,2′,3′‐lm]perylene (DIP) layer at the anode results in a very significant 60% increase in photocurrent owing to reduced exciton quenching at the anode. The simultaneous improvement of all three solar cell para­meters results in a power conversion efficiency of 6.4% for a non‐fullerene planar heterojunction cell.

Boron Subphthalocyanines as Triplet Harvesting Materials within Organic Photovoltaics

“…1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 4 In general, BsubPcs hold significant promise as organic electronic materials, 18 having been demonstrate as both electron donors, 19 electron acceptors, [20][21] and ambipolar interlayers 22 in singlet fission free organic photovoltaic devices. BsubPcs have been used with the complimentary absorbers α-sexithophene and subnaphthalcyanine chloride (Cl-BsubNc) to construct a planar heterojunction photovoltaic cell that absorbed a broad portion of the visible spectrum that also featured an energy cascade (transferring excitons from Cl-BsubPc to ClBsubNc within the cell) leading to a power conversion efficiency of up to ~8 %.…”

Degradation of Sexithiophene Cascade Organic Solar Cells

“…[5][6][7] Additional research focus lies on the development of alternatives to fullerene-derivative acceptors which are commonly used but provide limited absorption. [ 8,9 ] Cnops et al recently reported highly effi cient fullerene-free organic cascade devices employing the vacuum-deposited organic materials α-6T, SubPc, and SubNc as active layers. [ 10 ] Even though the layer sequence is simple using neither doped nor coevaporated layers, a maximum effi ciency of 8.4% has been achieved.…”

Open-circuit voltage exceeding the outermost HOMO-LUMO offset in cascade organic solar cells

“…Here, the limit to V OC has been ascribed to the HOMO-LUMO offset of the outermost semiconducting layers in the device stack [13] or alternately to the lowest value of DE DA at each interface [14]. Previous observations of V OC in cascade structures have found that adding an additional layer to a bi-layer cell, resulting in an energy loss step, does not reduce V OC appreciably [4,14]. However, others have observed the opposite [2,15] or mixed results [16,17].…”

“…One promising material system consists of organic semiconducting small molecules and/or polymers, although limitations inherent to their excitonic nature, such as low open-circuit voltage (V OC ) and poor coverage of the solar spectrum, must be overcome [1]. New device architectures employing multiple molecular species in a cascade energy alignment have begun to address these limitations, demonstrating impressive gains in efficiency by employing two donor materials [2,3], exciton blocking layers [4], interstitial layers at the donor-acceptor heterojunction [5e8], or directed energy transfer [9,10].…”