How to write R output with unequal length into excel

I have this R code to simulate time series data, the series have 5 colomns and 35 sub

N <- c(15L, 20L, 30L, 50L, 100L)
SD = c(1, 2, 3, 4, 5) ^ 2
theta = c(0.2, 0.4, 0.6, 0.8, 0.9, 0.95, 0.99)

res <- vector('list', length(N))
names(res) <- paste('N', N, sep = '_')

set.seed(123L)
for (i in seq_along(N)){
  res[[i]] <- vector('list', length(SD))
  names(res[[i]]) <- paste('SD', SD, sep = '_')

  ma <- matrix(NA_real_, nrow = N[i], ncol = length(theta)) 

  for (j in seq_along(SD)){
    wn <- rnorm(N[i], mean = 0, sd = SD[j])
    ma[1:2, ] <- wn[1:2]

    for (k in 3:N[i]){
      ma[k, ] <- wn[k - 1L] * theta + wn[k]
    }
    colnames(ma) <- paste('ma_theta', theta, sep = '_')
    res[[i]][[j]] <- ma
  }
}

res

** I EXPECT THIS**

v1  v2   v3  v4...v15  
1   4    3    1...1
2   6    3    2...2
3   8    3    12...5
4   4    4    8...5
5   6    4    4...5
6   8    4    0...5
7   4    5    2...5
8   6    5    1...2
9   8    5    2...2
10  11   12   13...2
11  12   13   14...4
8   6    5    1...4
9   8    5    2...4
10  11   12   13...4
11  12   13   14...4

I want to write res into any of the excel file. It could be .csv file. I want 1 in one cell, 2 in one cell etc and not 12345 put together in a cell.

After then I write it to an excel file