Light intensity modulated photoluminescence for rapid series resistance mapping of perovskite solar cells

They enjoy high optical absorption, nearideal band gaps, high carrier mobilities, and long carrier diffusion lengths. [1][2][3][4][5][6] Meanwhile, this class of materials consists of Earth-abundant elements and is solution-processable, making it a low-cost material. [7,8] At present, sandwich structure perovskite solar cells (PSC) have demonstrated power conversion efficiencies (PCE) as high as 25.7%, only 0.4% behind monocrystalline silicon. [9] However, there has been growing interest in PSC with a back-contact architecture due to various advantages in the design compared to sandwich PSC. A key improvement is the enhanced light harvesting, due to the elimination of the front contact and its parasitic light absorption. This offers the opportunity to employ an anti-reflective coating and a front-textured perovskite layer. [6] Drift-diffusions simulations reveal an improvement in photocurrents by ≈20% [10] and with further optimization, the PCE of back-contact PSC is expected to exceed their sandwich structure counterparts. [11,12] This has already been demonstrated in the case of silicon-based devices, with champion silicon back-contact solar cells enjoying a PCE of 26.6%. [13] There has also been growing interest in PSC with a back-contact architecture as a component in tandem cells in order to exceed the Shockley-Queisser (SQ) limit of a single junction. [14,15] To date, the stabilized PCE for back-contact PSC has reached 11.5 and 9.1% for single and poly-crystalline perovskite-based devices, respectively. [16,17] While short-circuit current densities (J SC ) have exceeded 20 mA cm −2 for poly-crystalline PSC, the reported fill factors (FF) ≤ 0.56 and open-circuit voltage (V OC ) ≤ 1.06 V have been underwhelming. [17][18][19][20][21][22][23][24][25][26][27] Low FF is typically attributed to poor carrier transport and excessive recombination in the absorber layer and/or across the perovskite/transport layer interfaces. [28] Recently, our group has demonstrated that the incorporation of a mesoporous TiO 2 layer, which increases the interfacial contact area, improves charge extraction resulting in significant increases in the J SC and FF of 36 and 25%, respectively. [17] The low V OC indicates high non-radiative recombination rates. Recently, Tainter et al. [27] reported on back-contact cells that enjoy long diffusion lengths (≥12 µm), slow surface recombination velocities ≈2 cm s −1 with short circuit currents of 18.4 mA cm −2 (external quantum efficiency (EQE) of 70%) but a meager V OC = 0.57 V. They propose the limiting factor in their devices to be high dark saturation currents, a parameter that The efficiency of back-contact perovskite solar cells has steadily increased over the past few years and now exceeds 11%, with interest in these devices shifting from proof-of-concept to viable technology. In order to make further improvements in the efficiency of these devices it is necessary to understand the cause of the low fill factor, low open-circuit voltage (V OC ), and severe hysteresis. Here a time-dependent...

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“…In future works it would be possible to map the series resistance using voltage‐dependent PL. [ 51 ]…”

Section: Resultsmentioning

confidence: 99%

Ideality Factor Mapping of Back‐Contact Perovskite Solar Cells

Rietwyk

Lin

Tan

et al. 2023

Advanced Energy Materials

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“…It is noteworthy that it is also possible that such regions have a current extraction level dependent R s . [ 48 ]…”

Section: Resultsmentioning

confidence: 99%

“…[ 39,40 ] They have been also used to image i V OC , [ 41–45 ] spatial variation of the optical bandgap, [ 46 ] current transportation, [ 12,44 ] and R s . [ 47,48 ]…”

Section: Introductionmentioning

confidence: 99%

Contactless Series Resistance Imaging of Perovskite Solar Cells via Inhomogeneous Illumination

et al. 2021

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A contactless effective series resistance imaging method for large‐area perovskite solar cells that is based on photoluminescence imaging with nonuniform illumination is introduced and demonstrated experimentally. The proposed technique is applicable to partially and fully processed perovskite solar cells if laterally conductive layers are present. The capability of the proposed contactless method to detect features with high effective series resistance is validated by comparison with various contacted mode luminescence imaging techniques. The method can reliably provide information regarding the severeness of the detected series resistance through photoexcitation pattern manipulation. Application of the method to subcells in monolithic tandem devices, without the need for electrical contacting the terminals, appears feasible.

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“…This approach therefore only provides information integrated over the entire device area. A range of techniques have been established for spatially resolved analysis of photovoltaic devices 1,2 such as light-beam-induced current mapping (LBIC), [3][4][5] lock-in thermography (LIT), [6][7][8] photoluminescence (PL) imaging, 3,[9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] and electroluminescence (EL) imaging. 25 However, as further discussed in the supplemental information (section A), these techniques can either probe only a portion of the local J(V) characteristics or require numerical fitting to a postulated diode model.…”

Section: Introductionmentioning

confidence: 99%