Anion‐Doped Thickness‐Insensitive Electron Transport Layer for Efficient Organic Solar Cells

Abstract

In organic solar cells, interfacial materials play essential roles in charge extraction, transportation, and collection. Currently, highly efficient and thickness-insensitive interfacial materials are urgently needed in printable large area module devices. Herein, water/alcohol-soluble conjugated polyelectrolyte PFNBT-Br, with medium bandgap based on benzothiadiazole, are doped by two alkali metal sodium salts, NaH 2 PO 2 , Na 2 C 2 O 4 with different counter anions, to pursue high efficiency and thickness-insensitive electron-transport layers. Results show that the doping of electron-transport material can effectively promote the performance of the devices. Moreover, electron-transport layers doped by these salts with different counter anions show different behaviors in performances. Among which, the salt with oxalate anion C 2 O 4 2− (also named Ox 2− ) shows much better device performance than the salt with hypophosphite anion (H 2 PO 2 − ), especially under the thick film condition (e.g., 50 nm). The greatly enhanced performances of interfacial material doped by Ox 2− are due to reduced series resistance between the active layer material and the electrode, reduced dark-current, improved charge transport, and extraction efficiency, and decreased charge recombination for the devices at thick-film condition. These results demonstrated that n-doping could be a great potential strategy for making thickness-insensitive interfacial layers, besides, the performances can be further improved by carefully selecting salts.

Interface Engineering for Highly Efficient Organic Solar Cells

“…Based on this, Liu et al fabricated OSCs device and doped PFNBT‐Br with NaH 2 PO 2 or Na 2 C 2 O 4 . [ 236 ] Both doped WSCPs showed improved device performance as compared with un‐doped controls. Moreover, the devices with Na 2 C 2 O 4 ‐doped CILs showed higher thickness tolerance relative to CILs doped by NaH 2 PO 2 , benefiting from the stronger doping capability of oxalate multivalent anions.…”

Trade‐Off Break between the Crystallinity and Phase Separation of Donor/Acceptor via a General Two‐Dimensional Transition‐Metal Phosphorus Trichalcogenides Nanoparticle Dopant Concept for Efficient and Stable All‐Polymer Solar Cells

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Organic solar cells (OSCs) have received colossal attention in the academic community because of their splendid advantages such as flexibility, [1,2] translucency, [3] lightweight, [4,5] and non-toxicity. [6][7][8][9] In the bygone 15 years, OSCs obtained remarkable progress in device engineering, [10][11][12][13] materials design, [14][15][16][17] and mechanism explore, [18][19][20] and the first-class certified power conversion efficiency (PCE) of OSCs has surpassed 19%. [21][22][23][24] Among currently constructed OSCs, all-polymer solar cells (all-PSCs) exploiting conjugated polymers as donor/ acceptor (D/A) demonstrate unique advantages, such as mechanical tolerance, high tolerance to D/A mixing ratios, and excellent thermal and photo stability, which makes all-PSCs more competitive when integrated into wearable and portable electronics applications.

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