Joydeep Bhattacharya

A photonic-plasmonic structure for enhancing light absorption in thin film solar cells

We describe a photonic-plasmonic nanostructure, for significantly enhancing the absorption of long-wavelength photons in thin-film silicon solar cells, with the promise of exceeding the classical 4n2 limit for enhancement. We compare identical solar cells deposited on the photonic-plasmonic structure, randomly textured back reflectors and silver-coated flat reflectors. The state-of-the-art back reflectors, using annealed Ag or etched ZnO, had high diffuse and total reflectance. For nano-crystalline Si absorbers with comparable thickness, the highest absorption and photo-current of 21.5 mA/cm2 was obtained for photonic-plasmonic back-reflectors. The periodic photonic plasmonic structures scatter and reradiate light more effectively than a randomly roughened surface.

Photo-induced changes in fundamental properties of organic solar cells

We report on the measurement of fundamental properties such as deep defects and hole mobility in poly-3-hexyl-thiophene (P3HT)/[6,6]-phenyl-C60-butyric acid methyl ester(PCBM) solar cells when the cells are exposed to solar radiation without any atmospheric exposure. It is found that the midgap defect density in P3HT and the interface density between P3HT and PCBM increase significantly upon light soaking along with a reduction in hole mobility in P3HT. The increase in defect density leads to a corresponding increase in reverse saturation current of the diode, and the corresponding decrease in open circuit voltage of the cell upon light soaking.

Monetary, Fiscal, and Reserve Requirement Policy in a Simple Monetary Growth Model

The authors consider an otherwise conventional monetary growth model in which spatial separation and limited communication create a transactions role for currency, and stochastic relocation gives rise to financial intermediaries. In this framework they consider how changes in fiscal and monetary policy, and in reserve requirements, affect inflation, capital formation, and nominal interest rates. There is also considerable scope for multiple equilibria; the authors show how reserve requirements that never bind along actual equilibrium paths can play an important role in avoiding undesirable equilibria. Finally, they demonstrate that changes in (apparently) nonbinding reserve requirements can have significant, real effects. Coauthors are Mark G. Guzman, Elisabeth Huybens, and Bruce D. Smith. Copyright 1997 by Economics Department of the University of Pennsylvania and the Osaka University Institute of Social and Economic Research Association.

Fertility choice under child mortality and social norms

In most demographic transitions, declines in child mortality precede declines in net fertility rates. Variants of the Barro–Becker model of fertility fail to deliver this link. A simple extension, the inclusion of social norms regarding fertility, generates the desired effect.

Unfunded Pensions and Endogenous Labor Supply

Abstract. A classic result in dynamic public economics, dating back to Aaron (1966) and Samuelson (1975), states that there is no welfare rationale for PAYG pensions in a dynamically-efficient neoclassical economy with exogenous labor supply. This paper argues that this result, under the fairly-mild restriction that the old be no less risk-averse than the young, extends to a neoclassical economy with endogenous labor supply.

Choosing to Keep up with the Joneses

Does a rise in income inequality induce people to work harder to stay in the rat race (“keep up with the Joneses”) or to simply drop out? We investigate this issue in a simple new framework in which heterogeneous ability agents get extra utility if their consumption keeps up with the economy’s average. The novelty is that agents are allowed to choose whether they want to stay in or drop out of the rat race. We show that sufficiently high ability agents choose to keep up with the Joneses and they enjoy higher consumption but lower leisure than those who don’t. When income inequality rises in a mean-preserving manner, average leisure in the economy may fall. Our analysis touches on the question, why are Americans working so much compared to the Europeans? We posit that higher income inequality in the US, by inducing more people to join the rat race there, may be partly responsible for the transatlantic leisure divide.

Who is Afraid of the Friedman Rule

We explore the connection between optimal monetary policy and heterogeneity among agents. We utilize a standard monetary economy with two types of agents that differ in the marginal utility they derive from real money balances-a framework that produces a nondegenerate stationary distribution of money holdings. Without type-specific fiscal policy, we show that the zero-nominal-interest-rate policy (the Friedman rule) does not maximize type-specific welfare; further, it may not maximize aggregate ex ante social welfare. Indeed one or, more surprisingly, both types of agents may benefit if the central bank deviates from the Friedman rule.

Aging, Unemployment, and Welfare in a Life-Cycle Model with Costly Labor Market Search

In recent years, many countries have experienced a significant shift in demographic patterns towards the elderly. This phenomenon poses numerous challenges for the design of public pension programs and labor market policies. To better understand how public policy should be designed in response to a aging workforce, it is imperative to first make an assessment of how the lifecycle affects aggregate labor market activity, and in particular, unemployment. While much work has been done on exploring how the lifecycle influences individual labor market behavior, its impact on aggregate labor market outcomes is far less studied. This paper is an attempt at addressing this lacuna within the context of a lifecycle model with costly search and matching in the labor market. The lifecycle of workers in conjunction with frictions in the labor market produces an environment in which unemployment arises as a natural possibility and both young and old workers find themselves contemporaneously competing for the same jobs. The lifecycle is shown to have significant implications for aggregate labor market activity; it may even be responsible for an inefficient allocation of workers to jobs. Additionally, public policies designed to increase labor market participation among older workers may not necessarily enhance aggregate welfare.

The Intergenerational Welfare State and the Rise and Fall of Pay‐as‐you‐go Pensions

This article develops a theory of the two‐armed intergenerational welfare state, consistent with key features of modern welfare arrangements, and uses it to rationalise the rise and fall in generosity of Pay‐as‐you‐go Pensions solely on efficiency grounds. By using the education arm, a dynamically‐efficient welfare state is shown to improve upon long‐run laissez faire even when market failures are absent. To release these downstream welfare gains without hurting any transitional generation, help from the pension arm is needed. In the presence of an intergenerational education externality, pensions initially rise in generosity but can be replaced by fully funded pensions eventually.

Sub-optimality of the Friedman rule in Townsend's turnpike and stochastic relocation models of money: Do finite lives and initial dates matter?

The Friedman rule, a widely studied prescription for monetary policy, is optimal in Townsends turnpike model of money; it is not so in the overlapping generations version of his stochastic relocation model of money. We investigate these monetary models in the light of this disparity. To that end, we create a modified version of the turnpike model that generates the same stationary monetary equilibria as does the two-period overlapping generations model with random relocation. We exploit this equivalence to explain the aforementioned disparity. We also discuss the importance of whether or not the economy has an initial date.